50% of engineers graduated in the bottom half of their class

[Vern Heiler]

"50% of engineers graduated in the bottom half of their class". to quote Stacey Van Houston on another thread.

Pre-drywall inspection today I observed three truss top cords sagging like the US economy. Trusses are supporting the valley, above the front entry. I'm no engineer but 8-9' unsupported span of 2x4 truss cord seems a little long without having a roof valley on top of it.

The worst part is this is a model that they have sold many times in this large retirement community. When I recommend "further evaluation by licensed engineer", it may be the same engineer who designed it. What then?

[Randy Mayo]

Vern

Is it possible some trusses were placed out of order?

In your first picture the trusses to the left of the ones sagging have extra web members to support mid span loading with no apparent load on them. Its not unusual for trusses of common span length to be interchanged with ones of like span but with with different web configurations (not good).

Don't be so quick to blame the engineer when the truss layout details were probably given to the prime contractor who may or may not have given them to the framing subcontractor who may or may not have given them to his layout man who asked some poor 18yr old laborer to go get the next 40' truss out of the stack. It would take some in depth investigating to sort out the blame which may be placed on one individual or may be spread out over several individuals.

By the way that was a good catch on your part the average inspector would have missed that.:)

[Vern Heiler]

Vern

Is it possible some trusses were placed out of order?

In your first picture the trusses to the left of the ones sagging have extra web members to support mid span loading with no apparent load on them. Its not unusual for trusses of common span length to be interchanged with ones of like span but with with different web configurations (not good).



I thought about that. The trusses don't appear to be out of order as the first several span across the entry porch cover. I didn't see any way to rearange them to place support under the valley. For that matter I don't understand the purpose in so few web cords in the area above the left side of the kitchen and garage. (Note view from attic area)

[Jerry Peck]

And what about no post at that corner of the front porch?

Looks like the trusses and their bearing were designed to be supported by a post, which, if not present, would allow sagging, which would put more pressure on that valley.

[Vern Heiler]

And what about no post at that corner of the front porch?

Looks like the trusses and their bearing were designed to be supported by a post, which, if not present, would allow sagging, which would put more pressure on that valley.

If I remember correctly, the model home that the customer took me to see prior to the inspection, did not have a column supporting the cover. No matter how many pictures I take, its not enough. Just never thought I needed pic's of another house:( .

[chris mcintyre]

When I recommend "further evaluation by licensed engineer", it may be the same engineer who designed it. What then?

It will be, he (or she) will find something wrong with the install and try and put the blame in the framer. Spanning almost 9' with a 2x4 is ridiculous, but these track builders will find a company that is willing to stretch the limits of design to save 50.00 a house. Building codes are the maximum not the minimum for these companies.

If a different SE comes in they are reluctant to call out someone else's design, if a truss has been cut or needs modification they will give you a repair drawing but that is about it.

I know the sub division you were in, I was there last week, a friend of a friend is buying a house there, I was asked to come along "to see what you think". I could not tell him what I really thought, but more or less told him he was getting what he paid for. I did take some pictures, this was one of my favorites the plastic two piece tub!

[Jerry Peck]

If I remember correctly, the model home that the customer took me to see prior to the inspection, did not have a column supporting the cover. No matter how many pictures I take, its not enough. Just never thought I needed pic's of another house:( .


Would need more photos to tell ... :( ... but if one or both of those supports for the trusses were properly designed based on proper cantilevering out from inside (which I seriously doubt they were) - then no post would be needed as the load would be carried back inside and spread out to the rest of the roof and wall framing.

Just not enough in those photos to show it.

[Vern Heiler]

I know the sub division you were in, I was there last week, a friend of a friend is buying a house there, I was asked to come along "to see what you think". I could not tell him what I really thought, but more or less told him he was getting what he paid for. I did take some pictures, this was one of my favorites the plastic two piece tub!

Yup. Same tub, same 24" interior wall stud spacing.

[Mike Truss Guy]

"50% of engineers graduated in the bottom half of their class". to quote Stacey Van Houston on another thread.

That may be, but the chances are that most the bottom half do not pass the test to become practicing professional engineers. They probably become building inspectors. :p:D

Seriously though, 8' is about the max a high grade of 2x4 can span to support the vertical loads, but that is the span based on the plan view. The length of the 2x4 along the slope can be longer than that. Now wind loads are another matter. Personally I never like anything longer than and 8' span on the top or bottom although I have seen trusses in the field that are 20+ years old with 13' spans.

Also just because the engineer designs something does not mean the plant will follow the design exactly. I can't tell you how many times I see the as-built truss not like the design on paper. They leave off plates. They use the wrong lumber. They leave out webs. Anything that can go wrong has gone wrong. A good truss plant with a top notch QC department will catch most of the issues, but some always make it to the field and get installed.

[Nolan Kienitz]

.... and I would assume that the other 50% graduated in the top half :confused:

[Darren Miller]

I was thinking the same thing.....

[Jerry Peck]

.... and I would assume that the other 50% graduated in the top half :confused:


I've been WAITING for someone to point that out.

"50% of engineers graduated in the bottom half of their class"

If my math serves me "50% of the engineers" does indeed make up "half of their class". :D

My first thought was this:
- Q: What do you call a doctor who graduates at the BOTTOM of their class?
- A: "Doctor" :)

[chris mcintyre]

- Q: What do you call a doctor who graduates at the BOTTOM of their class?
- A: "Doctor" :)

And someone has an appointment with him in the morning!

(I am a huge fan of George Carlin)

[Denny Waters]

Proud Papa.
My son is graduating from UCDavis this spring. 3.5 gpa in mechanical engineering. Don't be too jelous, my other 14yr old is turning out to be the opposite.

[Gary Burnett]

Vern,
I noticed that was a Del Webb Community. I have done several inspections out at one here in Frisco, Tx. They may have been installed out of order. The first thing I noticed when I was in the attic was that they had actually engineered different trusses (additional webs with a larger opening in the center) to support the HVAC equipment. I was somewhat impressed with the fact they didn't let the HVAC guys just decide which ones to cut off for their install.

[Vern Heiler]

Vern,
I noticed that was a Del Webb Community. I have done several inspections out at one here in Frisco, Tx. They may have been installed out of order. The first thing I noticed when I was in the attic was that they had actually engineered different trusses (additional webs with a larger opening in the center) to support the HVAC equipment. I was somewhat impressed with the fact they didn't let the HVAC guys just decide which ones to cut off for their install.

Thanks for the reminder. I will try to follow up on this tomorrow and let everyone know how it turned out.

[Vern Heiler]

Engineers letter came back. Measured 1/2" bow in the top cord of two trusses. Repair is to scab a 2x4x12 to one side of each and nail at 6"oc throughought. Oh, it also says "Shore Truss and any supported spans in proper position as repair is made." I'll bet that happens!

[A.D. Miller]

Engineers letter came back. Measured 1/2" bow in the top cord of two trusses. Repair is to scab a 2x4x12 to one side of each and nail at 6"oc throughought. Oh, it also says "Shore Truss and any supported spans in proper position as repair is made." I'll bet that happens!

VH: Sounds like a classmate of the design firm's engineer.:D

[Vern Heiler]

VH: Sounds like a classmate of the design firm's engineer.:D

I don't know who he is but I've got his signature and stamp. I'm off the hook:) .

[chris mcintyre]

I'm off the hook:) .

...and so is the engineer.


Engineers letter came back.......Shore Truss and any supported spans in proper position as repair is made.

Now he can blame the carpenter.:rolleyes:

[Jerry Peck]

Engineers letter came back. Measured 1/2" bow in the top cord of two trusses. Repair is to scab a 2x4x12 to one side of each and nail at 6"oc throughought. Oh, it also says "Shore Truss and any supported spans in proper position as repair is made." I'll bet that happens!


...and so is the engineer.

Now he can blame the carpenter.:rolleyes:

Which is why I frequently say that engineer's letter is important, but THE important engineer's letter is the letter which states "The repair was done in accordance with the engineering design." and then the engineer signs and seals THAT letter.